(654g) Unveiling the Difference between CO2 and CO Reduction of Cobalt Phthalocyanine on CNT

Increasing global carbon emission has attracted broad concerns recently, and many alternatives have been studied to mitigate the situation. Electrochemical CO₂ reduction (CO₂R) towards valuable feedstocks has emerged as a promising approach to address the excessive concentration in atmosphere and thus help close the anthropogenic carbon cycle. Among various CO₂R pathways, methanol production is relatively uncommon, and only a few catalysts have been able to achieve the conversion. Cobalt phthalocyanine (CoPc), a well-known molecular catalyst, has been proved to be effective for CO₂R towards methanol when immobilized on carbon nanotubes (CNTs). However, the selectivity of CO₂R and CO reduction (COR) is demonstrated to be different.

In this study, we systematically evaluated the COR/CO₂R performance of CoPc@CNT in a flow cell under industrially relevant current densities. Our results showed that the faradaic efficiency of methanol in COR was about eight to ten times higher than that in CO₂R. We then investigated the CoN₄ structure using in-situ X-ray absorption spectroscopy (XAS) and monitored different reaction intermediates via in-situ attenuated total reflectance-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS).

Based on electrolysis experiments and mechanistic studies, we are able to reveal that the structure induced distinct selectivity of CO₂R and COR for CoPc@CNT in the flow cell. Overall, our findings suggest potential pathways of the mechanism of CO₂R and COR and provide new insights for understanding the structure-activity relationship of heterogeneous molecular catalyst.